As geometries continue to shrink, manufacturers often utilize optical techniques for performing non-destructive inspection and analysis of semiconductor wafers. Wafer test metrology equipment and techniques may often be used to verify that the wafer has not been damaged by previous processing steps as well as to measure alignment.
One critical process control technique used in the manufacturing of an integrated circuit may include the measurement of overlay accuracy between successive, patterned layers on a wafer. An additional process control technique may include the measurement of periodic structure alignment formed on a single layer formed by at least two separate processes.